1. Field of the Invention
The present invention relates to reciprocating cutting tools, such as band-held cutting tools called a “jigsaw”, and more specifically, to reciprocating cutting tools configured to cut workpieces by reciprocating blades.
2. Description of the Related Art
In general, a jigsaw includes a motion converting mechanism configured to convert a rotation of an electric motor as a drive source into a reciprocating motion of a blade, and a technology relating to this kind of motion converting mechanisms is disclosed in, for example, in US 2002/0032968A1 (also published as Japanese Patent No. 3710697).
The motion converting mechanism is assembled within an aluminum die-cast gear housing cover attached to a front portion of a body housing. The electric motor as a drive source is built in a tool body portion. The motion converting mechanism is configured to transmit the rotary output of the drive motor to a crank disk, cause a guide roller eccentrically attached to the crank disk to engage an angular U-shaped slider supported by the gear housing cover so as to be capable of making a vertical reciprocating motion, cause the guide roller to make an orbital motion in the slider while sliding therein and, using the vertical components of the orbital motion, cause the slider to make a vertical reciprocating motion, thereby causing a rod coupled thereto and the blade (cutting blade) mounted on the rod to make a vertical reciprocating motion.
The rod is coupled to the slider so as to be pivotable in the fore-and-aft direction with respect to the slider within a small angle, and the blade is pushed forward in a cutting direction by a backup roller. The backup roller is displaced in the fore-and-aft direction by the vertical motion of a cam plate in association with the rotation of the crank disk, so that an efficient cutting work is achieved by causing the blade to make the vertical reciprocating motion (orbital motion) while causing the same to pivot in the fore-and-aft direction.
However, the jigsaw in the related art described above has the following problems to be improved. In general, the hand-held tools of this type have a housing made of resin with a two-split structure for the purpose reduction in weight and cost. In the jigsaw described above, a resin made two-split housing structure is employed for the tool body portion in many cases. However, the gear housing cover having the motion converting mechanism built therein is formed of die-cast aluminum that is still heavy in weight. Regarding the gear housing cover, for example, since a smooth sliding motion of the guide roller with respect to the slider as well as a smooth vertical motion and a fore-and-aft reciprocating motion of the rod are required, related components are required to be assembled with a high degree of accuracy. Consequently, in the related art, the die-cast aluminum housing cover which can easily secure the accuracy by machining is attached to the inside of the body housing, and a pair of left and right guide rails configured to support the slider so as to be capable of making a vertical reciprocating motion are attached to the gear housing cover with a high, degree of accuracy. Therefore, the presence of the gear housing cover and the pair of left and right guide rails, which occupy large weight distribution ratios because of being formed of metal, makes the weight reduction of the entire jigsaw difficult.
Therefore, there is a need in the art for a reciprocating cutting tool that can be configured to have a lightweight construction.